Weighing scales:
a.&nbsp Shall be provided for weighing cylinders, at all plants using chlorine gas;
b.&nbsp Are required when hydrofluosilicic acid is used;
c.&nbsp Should be accurate to measure increments of 0.5 percent of load;
d.&nbsp Shall be graduated in pounds;
e.&nbsp Shall be required for volumetric dry chemical feeders;
f.&nbsp Are recommended for all other chemicals.

CENTER FOR DISEASE CONTROL (CDC)
Engineering and Administrative Recommendations for Water Fluoridation,
1995
"Day tanks or direct acid-feed carboys/drums should be located on scales;
daily weights should be measured and recorded. Volumetric measurements,
such as marking the side of the day tank, are not adequate for monitoring
acid feed systems."

"Scales
must be provided for weighing the amount of chemicals used in the dry
feeder."

AWWA MANUAL M4:
Water Fluoridation Principles and Practices, Third edition:
"In any fluoridation installation, except one based on a sodium
fluoride saturator, scales are necessary for weighing the quantity of
dry material to be used in preparing the solution, the quantity of solution
fed, or the quantity of fluoride compound or hydrofluosilicic acid delivered
by the appropriate feeder." -Page 26

"Alarms: To prevent underfeeding or loss of feed, alarm systems
can be included in either solution or dry feed systems. The alarm alerts
the operator when the level of solution in the day tank is low or when
it is time to add chemical." -Page 30

THE CHLORINE INSTITUTE
Pamphlet 1, "The Chlorine Manual"
"Weighing-Because chlorine is shipped as a compressed liquefied gas,
the pressure in a container depends on the temperature of the chlorine.
The pressure is not related to the amount of chlorine in the container.
Container contents can be determined accurately only by weighing."
–Page 10, Section 2.8.4

COMPRESSED GAS ASSOCIATION
CGA G-2 Manual
"Determining when cylinders are empty-Weighing. The best way to determine
if an ammonia cylinder is empty is to weigh it, without cap, and compare
the weight with the tare weight stamped on the cylinder." -Page 36,
Section 8.9.1

These documents may not represent a complete
list of regulations, recommendations or guidelines. Always consult your
local agencies to determine which specific guidelines, recommendations
or regulations affect your water or wastewater treatment operation.